Training for the 2025 TCS London Marathon with Stage 2 Endometriosis

My cycle comes before my training. Our 2025 TCS London Marathon runner Lillie Bleasdale is about to take on her fourth London Marathon, aiming for an incredible time of 2:55. She lets us in on her story battling stage 2 endometriosis while marathon training. 

Once the girl who dodged every PE class, she’s now lacing up for her fourth London Marathon, chasing her biggest goal yet: sub 2:55. But Lillie’s journey hasn’t always been about chasing faster times. Some races have simply been about showing up, reclaiming her body from a chronic illness that at times made it hard to put one foot in front of another, let alone run.

After years of unexplained pain and fatigue, she was diagnosed with endometriosis and adenomyosis, two chronic conditions that cause severe pelvic pain, exhaustion, and hormonal imbalances. Before her diagnoses, she often pushed through training despite nausea and fatigue that left her unable to finish runs. But following surgery and treatment, she gradually rebuilt her strength, determined to prove that with the right support, women’s bodies are capable of incredible things!

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Can you tell us how you got into running?

I was never a runner growing up! My mum wrote me a note to get out of PE at every available occasion. In 2016 I ran the London 10k and swiftly hung up my running shoes deciding this sport most definitely wasn’t for me. But then a year later, my Grandad passed, and my sister and I wanted to raise money for charity. The idea of us running seemed hilarious to most of our friends and family, so we turned it into a challenge: one race every month for a year. And that’s where I caught the running bug. By 2018, I’d run my first marathon, and I never looked back. Fast forward to 2020, post- pandemic, I qualified as a coach and PT, set up my own business - PASSA, and left my job. 

Tell us more about your coaching and PASSA!

My goal with PASSA was to create training plans that truly fit into women’s lives. I noticed many runners were following generic plans that didn’t take their lifestyles or need for strength training into account. Within months I had a growing community of incredible females, and that’s when I decided to dive deeper into how I could better support them, by adapting training to the different phases of their cycle and life.
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When did you first discover your diagnoses of endometriosis and adenomyosis? Can you explain what those two conditions are?

Endometriosis causes tissue similar to the uterine lining to grow outside the womb, leading to symptoms such as extreme pain, including during sex, extreme fatigue and brain fog. There is no known cause or cure, only symptom management. Adenomyosis is when the womb lining grows into the muscle of the uterus, and the only cure is a hysterectomy.

I’ve struggled with painful periods since the age of 12, and to manage this I was placed on the pill at 13. In 2020, my health took a turn, and I was then struggling with chronic pain and fatigue. After endless doctors’ visits, and very few answers, I started to do my own research. The symptoms I had been experiencing for years matched that of endometriosis. I pushed for a diagnosis but sadly with no luck so in 2021, I accessed private healthcare for a Laparoscopic Excision. Following this surgery I was diagnosed with stage 2 endometriosis in multiple places: my bowel, bladder, fallopian tubes and more - as well as being diagnosed with adenomysosis too. I started hormone treatment to put my body into a menopausal state to slow its regrowth and manage adenomysosis symptoms.

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What would you like to say to women who suspect they might be suffering from either endo or adenomyosis?

Advocate for yourself! Don’t take no for an answer, and don’t let anyone dismiss your pain as “just a bad period.” While it’s frustrating, start keeping a record of your symptoms, appointment notes, and reviews. Doctors often ask for a 3–6 month symptom diary, so starting this sooner rather than later can help speed up the process. Showing up to appointments armed with information gave me a much better chance of being heard.

Being diagnosed with these illnesses can seem isolating, especially with very little information available. I found huge support in online communities and connected with others who were experiencing the same symptoms, fighting for a diagnosis, and navigating treatment options. You are not alone in this.

What have been your greatest running successes?

The Chicago Marathon 2022 was my most pivotal race. It was just 10 months after surgery and my only goal was to be standing on that start line. I trained pressure-free for nine months, expecting to run a similar time to my previous marathon - but the race became a true demonstration of how much your life can change with the correct treatment of these illnesses. I achieved a 14.5-minute PB, running 3:07, something I’d only ever dreamed of. It felt like the start of a new life, where goals that once seemed impossible were now within reach. Since then, I’ve run two sub-3 marathons, and I still can’t believe that a body that once felt like it was against me can now achieve these things.

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What’s in your future as a runner? What are you aiming for next? 

I aim to push my marathon time down to 2:55 - this seems like a huge, huge goal, but I want to continue to prove to women that if we are listened to and treated correctly with these health conditions, we can truly be unstoppable forces.

Why London Marathon? What makes this race special?

The London Marathon is the marathon for me. This will be my fourth time running it and each one has been a truly different experience. In 2019, I ran for charity and enjoyed every single step. In 2021, I ran under a good-for-age bib, pushing through the most painful 26.2 miles of my life - one last race before my surgery and treatment. It was a proud yet truly painful experience. In 2023, my mental health wasn’t in the best place, and I struggled to keep my head screwed on. So in 2025, my only goal is to enjoy every step and be proud of whatever I achieve on the day. It really does feel like a homecoming.

Inspired to get out and run? See more from New Balance and the 2025 TCS London Marathon collection here.

Are you feeling inspired? Then join our SportsShoes Strava Run Club and become part of our inclusive community.
And for more inspirational tips to become stronger, better and happier, then check out our Motivation category. Because it’s no fun standing still.